The present invention relates to activating a pulsatile heart-lung bypass pump or an intra-aortic balloon pump on a patient whose heart is externally paced, and more particularly to a device for detecting optical signals emitted by the atrial or ventricular pace lights of a pacemaker and electronically converting those optical signals into electrical signals capable of activating the bypass pump or balloon pump.
Often it is necessary during surgery, particularly heart surgery, and during recovery from surgery to provide circulatory support for a weak or failing heart. This support can be provided by a bypass pump, preferably a pulsatile pump activated by an external pulse, or an intra-aortic balloon pump which is activated to deliver a counterpulse.
The success of the intra-aortic balloon pump counterpulsation technique largely depends upon the properly timed activation of the pump to deliver the counterpulse during the ventricular diastole portin of the cardiac cycle. Conventional methods of timing the counterpulsation include activating the pump in response to the atrial or ventricular waveforms of the patient's ECG trace or by application of the arterial pressure curve as a triggering-signal for counterpulsation. All of these signaling methods have disadvantages which can render counterpulsation ineffective when most needed by the patient.
When an atrial spike is present, the pump console will often recognize the atrial spike as well as the QRS complex of the ECG trace and may inflate the balloon twice instead of once during each cardiac cycle, making the assist-process ineffective. Combined application of atrial and ventricular pacing further complicates the matter by further increasing the number of electrical complexes which may trigger the pump. Additionally, inadvertent movement of skin electrodes under the surgical drapes or application of additional electrical devices in the operating room, such as electrocoagulation, can also severely disturb counterpulsation-circulatory assist during the period when it is needed the most by introducing noise and false signals into the counterpulsation triggering circuitry. Changes in the electronic circuitry of newer assist devices, such as the 950-ESIS modification of the KONTRON Model 10 pump marketed by Kontron Corp. of Everett, Massachusetts, altering the position of the sensor electrodes and bipolar atrial electrodes decreases, but does not fully eliminate these difficulties.
Recent application of the arterial pressure curve as the trigger-signal for counterpulsation excludes some of these false signals generated by the paced QRS complex or by an ECG tracing disturbed by other electric interference. This approach, however, has also several shortcomings. First, flattening of the arterial pressure curve due to hypotension or mechanical inadequacy of the pressure-sensing mechanisms, such as a clot or air in the line, makes sensing a trigger-signal impossible. Sensing a trigger-signal from the arterial pressure curve of patients who are being counterpulsated by either balloon-pumps or by specially designed heart-lung machines while being weaned off cardiopulmonary bypass is also extremely difficult. Because a portion of their cardiac output is still diverted through the extracorporeal circuit, their spontaneously generated pulse pressure may be very low and the electric signal generated will not provide an adequate trigger for counterpulsation. This problem receives further impetus by the increase in the application of partial cardiopulmonary bypass using various "non-traumatic" pumps. Also, the arterial pressure curve as the trigger for counterpulsation is often even more vulnerable to mechanical, electrical and electronic interference or noise, especially to electrocoagulation, than the ECG signal.
A pulsatile bypass pump similarly requires well timed activation in phase with the pumping of the patient's heart and is susceptible to the same problems associated with triggering a balloon pump.
The objective of the present invention is to minimize these serious problems in the management of critically ill heart patients.